As is often the case in the Bill Belichick era, the backfield is in a state of flux. Players going. Players coming. You name it. Uncertainty rules the day.

When New England (No. 2 in the AP Pro 32) was winning three Super Bowls in four years from 2002-2005, the team featured a power running game that could control the ball for long periods of time late in the game. Antoine Smith wasn't a Hall of Fame back, but he helped win two titles.

Now, there's a void. Despite a 13-3 regular season and an AFC championship last year, New England had problems keeping the ball away from opponents at the end of games. A strong, reliable running game would have helped that.

And then came the offseason. That's when Benjarvus Green-Ellis, the primary back for the past two years, departed for Cincinnati. What he left behind, is a stable of runners, sure.

But are any of them going to carry the load?

"We have a group of guys," second-year tailback Stevan Ridley said, "who are very much capable of that in our room."

Time will tell. New England opens the preseason Aug. 9 vs. New Orleans.

"Benjarvus was a great player for us," Ridley said, "but now, the next guy here has got to step up."

That might just be Ridley. He averaged 5.1 yards per rush in 87 attempts last season, and his 33-yard run was the team's longest of the season. Belichick lost some confidence in him, though, after fumbles against Buffalo and Denver late in the year.

"For me, I'm not a coach," Ridley said. "I went out there and played as best I could. Unfortunately, as a running back, you can never put the ball on the ground and that's something that I know, and that's been since pee-wee football."

He intends to keep the ball "high and tight" this season and "not repeat the same mistakes."

Veteran Danny Woodhead is most effective as a situational runner, usually from a passing formation. He appears to be the next Kevin Faulk, if you will, as an outlet on third down.

Second-year pro Shane Vereen was injured most of his rookie season, but he has also shown promise and can also catch the ball out of the backfield.

Undrafted rookie Brandon Bolden from Mississippi has been getting some reps, too, and could be the surprise that the undrafted Green-Ellis was.

"I think he seems like he's done a decent job in the areas that we've asked him to work in; special teams," Belichick said. "He can catch the ball, has some skill in the passing game and he had some production in the running game in college. We've only seen that in drills, we haven't seen that really in live competition yet. But based on college, it looked like he can run the ball."

Former Navy star Eric Kettani, who has served time on the practice squad, has completed his service obligations and is also in the mix.

For the first time since the productive Heath Evans left for New Orleans, the Patriots also have two, true fullbacks, Tony Flammetta and Spencer Larson, and that may help. In recent seasons, they have used linemen and tight ends as blocking backs in goal-line situations. Whether that signals a change in philosophy to more of a power running game remains to be seen.

As always with Belichick, anything is possible.

"We have had fullbacks in our offense, we haven't had fullbacks in our offense," director of player personnel Nick Cesario said. "Both of those guys are good football players in their respective roles, and we'll see how they do once we get to game situations."

Friday's practice was interrupted by two scuffles toward the end, the second time in three days players have gone at it. With temperatures in the 90s with high humidity, offensive lineman Ryan Wendell and linebacker Bobby Carpenter were the main combatants in the first tussle. A pair of rookie free agents — offensive lineman Darrion Weems and defensive lineman Marcus Forston — highlighted the second.

An irritated Belichick ordered everyone on the field to do three penalty laps, sparking a players meeting in the middle of the field, led by Brady. No word yet, on whether a primary ball carrier resulted in that meeting.

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NOTES: Brady celebrated his 35th birthday Friday. ... Offensive lineman Dan Connolly was overcome by the heat for a time during practice. ... Receiver Brandon Lloyd returned to practice after missing two days. ... The Patriots will be off Saturday, and begin preparations Sunday for the preseason opener. ... Tuesday's and Wednesday's practices will be shared practices with the Saints. ... Veteran guard Brian Waters has yet to report.